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Manuel,
?I hope I have as good luck as you did. My (2nd) QMX left the smoke out from the same 5 V p/s board. For me it destroyed C107 and Q108. The Zener doesn't quite seem right, but even if bad doesn't explain C107 going up in smoke. Doing lots of tests now to see if the main board has been damaged.?
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73, Dan? NM3A

I've been messing with electronics for most of my life both professionally and for fun. One rule I was taught early on is that you must always employ a current limiting PSU for any new build. Whiskers, misplaced components, dry joints and VERY VERY seldomly faulty components can be very depressing, 99% of the time the fault has always been of my own making and it's saved me on many an occasion.
For old mains transcievers and receivers I have a variac with 2 light bulbs in series. If there is a short, the bulbs burn brightly as you wind up the variac. It should be straightforward to build a low voltage version of the same, I might have a go at that.?

73s Ted?
2E0THH?

Manuel,
?I hope I have as good luck as you did. My (2nd) QMX left the smoke out from the same 5 V p/s board. For me it destroyed C107 and Q108. The Zener doesn't quite seem right, but even if bad doesn't explain C107 going up in smoke. Doing lots of tests now to see if the main board has been damaged.?
--
73, Dan? NM3A

Hi Dan,

I?m not 100% sure, what was the cause in my case, so I can only guess.

But I would look at the real obvious stuff:
- I?ve shortened some of the display wires and gave them another touch with soldering iron, so it would not short to anything surrounding
- I bended the "mentioned in assembly manual" display clamp flat, that would have contact to mainboard otherwise?
- I had obvious dry solder joints on one of the filters (just pre-soldered for positioning, not heated through)
- Take special care of the short between DC in and left rotary (That should be mentioned in the manual in RED when assembly of mentioned components is advised, not just later in final check)

Hans? Tetris games are always admirable and I can?t wrap my head around how he keeps coming up with stuff like this. I love it,? but it comes at a price.
The price is: You need to check for problems 3D, no longer just 2D......

73 Manuel; DL2MAN

On Wed, Aug 2, 2023 at 10:42 PM, Ted 2E0THH wrote:

I've been messing with electronics for most of my life both professionally and for fun. One rule I was taught early on is that you must always employ a current limiting PSU for any new build. Whiskers, misplaced components, dry joints and VERY VERY seldomly faulty components can be very depressing, 99% of the time the fault has always been of my own making and it's saved me on many an occasion.
For old mains transcievers and receivers I have a variac with 2 light bulbs in series. If there is a short, the bulbs burn brightly as you wind up the variac. It should be straightforward to build a low voltage version of the same, I might have a go at that.?

73s Ted?
2E0THH?

The Lab Power Supply was a very early investment in the uSDX / (tr)uSDX development path, and it paid for itself multiple times.....
If you?re a maker, you need one. Can?t put enough emphasis on that recommandation.
Especially considering the fact, that I bought mine for 60€ in a Reichelt Sale. They?re absolutely not expensive.
Right now, they sell it for 74,43€ (I have a "Peak Tech 6080A")

73 Manuel; DL2MAN

After reading Hans? Article on SMPS Fail for Voltage jump, and seeing his findings about D108 failing all the time, I might have been victim of that effect, too:
/g/QRPLabs/message/106566
I increased Voltage on my Lab Power Supply before from 9-12V. Not in a sudden jump, but slowely while monitoring.
But the effect was the same: D108 died and pulled 5V Line down to GND, protecting the rest of the circuit....

73 Manuel; DL2MAN